Not applicable.
The present invention relates to torsional joint assemblies and methods of making same and more particularly to a joint assembly having a singularity-free joint.
Various techniques are known in the art to form torsional bonded joint assemblies using dissimilar materials. Unfortunately, typically even in good designs there are some small zones along the joint where the stresses are very high. These zones are typically located where the bonding surface reaches the outer or the inner surface of the assembly, and also where the adjacent surfaces create the angles. When the linear elasticity theory is used for mathematical modeling of the assembly, these zones manifest themselves by presence of so called singularity points where the stresses become infinitely large. In reality, if the applied load is high, the material fails at the vicinity of the singularity points and the fracture surface may then propagate through the assembly resulting in the complete structure failure. For moderate loads, the stresses near the singularity points may reach the plasticity limit and the material experiences plactic deformation, leading to crack initiation and growth.
Therefore, it would be advantageous to have a torsional joint assembly which is free of such singularity points.
The present invention relates to a joint assembly and method of making same that includes securing surfaces that are specially configured to essentially eliminate singularity points along the securing joints thereby facilitating an extremely strong bond with a relatively short joint length.
The invention also includes a general purpose joint assembly for co-axially connecting cylindrical members which are formed of different materials having different shear modulai, the assembly essentially eliminating stress singularities along the joint. In one embodiment, the assembly includes a first tubular member formed of a first material having a first shear modulai. The first member is formed around an axis and has a proximal edge at a proximal end and has internal and external surfaces, the internal and external surfaces each being first surfaces. One of the first surfaces forms a first proximal surface at the proximal end, at least a portion of the first proximal surface sloped radially to the proximal edge so as to define a first angle with respect to the axis.
A second tubular member is formed of a second material having a second shear modulai. The second member has a proximate edge at a proximate end and has inner and outer surfaces, the inner and outer surfaces each being second surfaces. One of the second surfaces forms a proximate surface at the proximate end and the other of the second surfaces forming an incline surface. The proximate surface includes second proximal and second distal surfaces, the second proximal surface separating the second member from the second distal surface. The second distal surface slopes radially to the proximate edge such that the second distal surface conforms to the first proximal surface. At least a portion of the incline surface slopes radially to the proximate edge so as to define a second angle with respect to the axis. The second proximal surface is parallel to the incline surface. The first proximal and second distal surfaces are secured together by an adhesive layer wherein, the first and second angles are a function of the shear modulus. Preferably, in applications providing a thermal barrier, the first material is a glass-epoxy composite and the second material is a metal.
In one embodiment the external surface forms the second distal surface, the inner surface forms the first proximal surface and the outer surface forms the incline surface.
Thus, another object of the invention is to provide a general, all purpose joint configuration for joining two cylindrical member at their ends in a manner which essentially eliminates singularity points along the length of the joint. This is accomplished by choosing bonding angles as a function of various material characteristics as described in detail below.
It is yet another object of the present invention to provide a joint assembly where members of dissimilar material can be bonded in numerous manners including the use of adhesive, as well as brazing, soldering and other bonding techniques, such as in the case of bonding dissimilar metals together.
These and other objects, advantages and aspects of the invention will become apparent from the following description. In the description, reference is made to the accompanying drawings which form a part hereof, and in which there is shown a preferred embodiment of the invention. Such embodiment does not necessarily represent the full scope of the invention and reference is made therefor, to the claims herein for interpreting the scope of the invention.